As is known in the art, cabinets, such as those used to store electrical components require internal cooling. Typically fans are used to blow air from outside the cabinet into the cabinet and over the electrical components and then exhaust the air.
In some such cabinets the electrical components are electrically interconnected in the cabinet through an internal backplane. In many cases, the system operates with a single voltage (e.g., +12V) power source. Further, the current carrying capacity of the backplane is typically determined by the requirements of the system.
One such system is shown in FIG. 1. Here, a power supply module is connected to a fan through a backplane. Also connected to the backplane are other electrical components here mounted to printed circuit boards that plug into the backplane. The power supply module includes, in this example, a 12 volt, 2 amp power supply. A fan module having a fan for cooling the electrical components is powered by the 12 volt 2 amp power supply, it being noted that the backplane is in this example designed to handle a maximum of 2 amps of current. The fan produces a pulse train shown in FIG. 1A having a frequency or pulse repetition rate, proportional to the fan's rotational speed. Such information is useful in controlling the fan and for monitoring whether the fan is operating properly. In any event, the speed of the fan is monitored by a pulse sensor in the power supply module.
As is also known systems may be designed to be expanded in capacity or processing power. For example, with a data storage system, it may be required to increase the storage capacity or processor capability. That is, it may be required to have additional components plugged into the backplane, or raise the power dissipation of replacement upgrade components. Increasing the capacity of the system results in higher cooling requirements within the cabinet i.e., increased power for the fans. Since in many systems, the fans are powered by the voltages on the backplane. Thus, the increase in capacity may result in the backplane having to handle more current for the additional cooling than the original maximum current handling capacity of the backplane. Replacement of the backplane to accommodate this increased current handling capacity may be impractical and costly.